Injection liner

ABSTRACT

A replaceable injection liner for a gas chromatograph is disclosed having a laterally extending external flange at its input end against which an injection septum is placed. A closure cap is positioned over and around the external flange and the injection septum to seal the septum against the flange, the septum closing and sealing the input end of the injection liner. The liner has a seal positioned beyond the flange to seal the interior surface of the injector and isolate it from the atmosphere and the injector&#39;s internal pressure.

This invention is concerned with an injection liner, and relates inparticular to a novel form of liner utilisable with a septum and cap andintended for use in the injector of a gas chromatograph.

Gas chromatography is a technique widely employed in industry. It findsparticular application in the fields of medical care, pharmaceuticalanalysis, petroleum chemistry, petrochemicals and environmentalanalysis, and is especially valuable for the separation of complexmixtures into their components, typically such mixtures as containorganic chemicals, either as a simple mixture or in a solvent, such aswater.

Basically, chromatography involves the transferring of a mixture ofmaterials (the “sample mixture”) by means of a flowing medium (the“mobile phase”) along a passageway (the “column”) containing a substance(the “stationary phase”) to which the different components of themixture are weakly, but differentially, attracted, so that gradually theless attracted components get ahead of the more attracted ones, andeventually, if the column is long enough, they are completely,separated. It is called “chromatography”—colour writing—after itsoriginal use, which was to separate mixtures of coloured dyes. In thecase of gas chromatography, the mobile phase is a gas.

There are a number of different types of gas chromatography, but thosein common use employ as the column a long tube containing the stationaryphase. There are several designs of column, but typically it is long,narrow tube made from fused silica (like glass) coated on the outsidewith a polyimide or similar plastic layer to prevent corrosion and addstrength. The silica tube may typically be from 5 to 50 meters (about 16to 160 ft) long, and be of internal diameter 100 to 750 microns(0.0001-0.00075 m, or 0.01-0.075 cm, or about 0.004-0.03 in). Thestationary phase chemical is either bonded on the inside of this tubeor, in some cases, is deposited on solid, porous inert support materialswhich fill the tube.

When a small amount of the sample mixture is introduced to the inlet endof the column, with the mobile phase passing from the inlet end of thecolumn to the outlet end, the mixture is blown slowly through thecolumn. The stationary phase selectively slows down some of thecompounds in the sample mixture, whereas other compounds are slowed muchless or not at all. Compounds that are not slowed travel at the speed ofthe mobile phase, while compounds that are slowed down travel moreslowly than the mobile phase. Because some compounds are slowed down andothers are slowed less, those which are slowed less emerge from the farend of the column before those which are slowed more. Thus the mixturebecomes separated into (some of) its components

In operation, a very small amount of the sample mixture—typically onemilligram or less—is injected into the inlet end of the column which issealed into ant elongate tubular device called an injector. The injectorfacilitates the introduction of this small amount of sample into thesystem, provides the required carrier gas flow for the column, and mayalso perform other functions, including the evaporation andconcentration of the sample. Gas from the injector flows through thecolumn from the inlet, injector end, and the individual components ofthe mixture emerge separately from the outlet end of the column at atime that depends on the velocity of the carrier gas and the extent towhich the components are slowed by the stationary phase.

These separated compounds are then passed into a device called adetector, which can simultaneously detect the presence of the componentsand, in general, measure the amount of each one present. The detectorproduces an electrical signal that is amplified and passed todata-processing equipment which measures both the time after injectionthat the component emerged from the column and also the amount of signalproduced; it can then produce a report on the composition of theoriginal mixture, which can be utilised by the User to determine whatactions, if any, should be taken.

There are several points in this analytical process at which errors canbe introduced. Two of these are at and before the point of injection.

Sample mixtures may be derived from a number of sources, and may requirea variety of preparations, including concentration, extraction andreaction. In order to maintain the integrity of the sample, these stepsare kept to a minimum and, wherever possible, they are automated. It isalso important that the skill level of those preparing the samples doesnot affect the integrity of the results.

Samples may also be dirty. That is, they may contain materials thatremain in the injector, may not pass through the column at all, or maycontaminate the detector. Such materials can cause the deterioration ofthe results of subsequent analyses.

To overcome some of these problems, injection liners are frequently usedin the injector of the chromatography An injection liner is a narrowtube that fits inside the injector interior, literally providing a linerfor the injector, and samples are injected into this liner tube ratherthan directly into the injector itself. Materials that would remain inthe injector are thus deposited and remain in the liner instead, andwhen the liner becomes too contaminated with these materials it can beremoved and replaced with a new liner.

Injection liners may also deliberately contain materials thatselectively hold back compounds, by chemical or physical processes.These materials are called packing materials, and are able selectivelyto absorb specific components of the mixture.

In some instances the absorption of components in the liner packingmaterial is reversible. That is, a material may be absorbed at a lowtemperature, and may thereafter be released by raising the temperature.One such packing material absorbs organic components at a lowtemperature, but allows water to pass freely through it at the same lowtemperature; the water can thus be diverted out of the system whilst theorganic materials remain within the packing material. Subsequently, thegas flows within the system can be redirected, and the liner and itscontents heated up so that the organic materials are then displaced intothe column for analysis.

However, the liners themselves become contaminated, and need to bechanged from time to time. This is frequently a difficult process, andone that is also very difficult to automate. It involves first coolingthe injector, and then reducing the gas pressure in the chromatographysystem. When the pressure inside the injector is at atmosphericpressure, the top of the injector is opened. The top of the injectorgenerally has a number of pipes attached to it. Getting the top off withthe pipes attached is an operation requiring considerable operator skilland dexterity. Once the top is out of the way, the liner can be pulledout and removed. A new liner must then be placed in the injector, andthe above process repeated in reverse before the next analysis can bestarted.

This replacement process involves significant skills and a number ofsteps at which leaks and other errors can be introduced. The process isalso very difficult to automate. Even in an otherwise automatic system,the replacement of the liner tends to be a manual operation. This means,unfortunately, that very often the liner is left in place far longerthan it should be, leading to deterioration of the performance of theinjector, possible degradation of samples in the injector, and potentialerrors in the results presented to the analyst.

The present invention proposes a novel type of injection liner that canmore easily be replaced either manually or automatically. Morespecifically, the invention suggests an injection liner the input end ofwhich has a laterally-extending external flange against which in usethere can be placed an injection septum for closing and sealing theinput end, which septum is then sealed in place against the flange by aclosure cap that fits tightly over and around the two. For use with aninjector that itself directly supplies the carrier gas, the linercarries sealing means beyond the flange which can in use form a sealagainst the interior surface of the injector, so separating this regionfrom the atmosphere and also from the injector's interior pressure.

In one aspect, therefore, the invention provides an injection liner foruse in the injector of a gas chromatograph, the liner being in the formof an elongate tube having an input end and an output end,

the input end bearing a laterally-extending external flange againstwhich in use there can be sealed an injection septum closing the inputend, a closure cap then fitting tightly over and around the septum andthe flange so as to hold the septum in place.

The invention also provides the “use” combination of liner tube, septumand cap. Thus, it provides an injection liner in the form of an elongatetube having an input end and an output end, the input end bearing alaterally-extending external flange, and the liner including

an injection septum, for fitting over the input end and sealing againstthe flange, and

a closure cap for fitting tightly over and around the septum and theflange so as to hold the septum sealingly against the flange and closethe input end.

The invention provides an injection liner for use in the injector of agas chromatograph. The idea of gas chromatography, and of the injectorused as part of the apparatus, and the utilisation of a liner for theinjector, has been discussed hereinbefore, and needs no further commentat this time, save perhaps to note that the chromatograph may be one ofthose where the carrier gas flow has to be fed into the liner via anarrow tube passing through the septum or it may be one of those wherethe injector can be modified to supply the gas directly, and it passesinto the liner through a special input aperture positioned between itsends and on the atmosphere side of the sealing means which seals theliner to the inside of the injector. This is discussed furtherhereinafter.

The invention's injection liner is in the form of an elongate tubehaving an input end and an output end. Although the dimensions of linersare chosen to fit the injectors with which they are to be utilised, atypical such liner is 80 mm (3.2 in) long with an internal diameter of 3mm (⅛ in) and an external diameter of 5 mm (0.2 in), and is made of aborosilicate glass such as PYREX (Registered Trademark).

The liner's input end carries the flange against which the septum seals;the output end—or, rather, a short length of the tube leading to theoutput end—may conveniently be associated with a restriction either toimprove the liner's ability to retain packing materials which may beplaced therein, or to improve its ability to induce gas flows within itwhich encourage desired flow patterns, or both. Such a restriction can.take many forms; for instance, the tube may be internallynarrowed—profiled—to provide one or more, step or waisted portion, orthe tube may be blocked with a porous plug.

The input end of the liner of the invention bears a laterally-extendingflange—an outwardly-directed one—against which there can in use besealed an injection septum closing the input end. The flange need not bevery deep, provided it can support the septum pushed against it; asimple lip of three or four millimetre (an eighth of an inch or so) isusually sufficient. The flange is conveniently given a number ofconcentrically-circular ridges on its septum-facing surface so as in useto assist in maintaining a gas-tight seal between the septum and theflange.

In use, the liner's flanged output end has sealingly positioned againstit an injection septum closing the input end. The purpose of thisseptum, a disc-like object matching the dimensions of the liner'sflanged input end, is to close that input end while at the same timeallowing a sample (of the material to be analysed) to be injected intothe liner through the septum using a syringe-like object fitted with afine needle that can be pushed through the septum and then withdrawntherefrom without leaving any significant hole. The septum musttherefore be made of a rubbery material; a preferred such material is asuitable silicone rubber, and advantageously this is protected by acoating on each side in the form of a thin layer ofpoly-tetrafluoroethylene (PTFE).

In use, the septum closing the liner's input end is held in place with aclosure cap fitting tightly over and around the septum and the flange.The cap can be screwed on (the exterior edge of the flange canconstitute a suitable thread), it can be a shrink-fit over the septumand flange, or it can be crimped on (that is, be held tightly in placeby distorting the material of the cap below the flange).

The cap may be made from, or enclose, magnetic material to assist in themanual or automatic removal and replacement of the liner, when required.

Conveniently, the cap extends in use laterally beyond the boundaries ofthe tube and flange, and can be used to provide a sealing surfaceagainst the input end of the injector.

Where—as noted hereinbefore—the liner is to be employed with achromatograph which is one of those where the injector is able to supplythe carrier gas directly, the liner includes a special gas inputaperture positioned between its ends (and usually closely adjacent theinput end), and between this aperture and the liner's output end thereis sealing means which in use seals the liner to the inside of theinjector. The sealing means is preferably an O-ring, suitably mountedaround the exterior of the liner within a groove, or between wall-likeridges effectively defining such a groove, in/on the outside of theliner.

When in place in the injector, the liner may be held sealed in place bya downward force on the liner. This force would maintain the sealbetween the gas pressure inside the injector and the pressure of thesurrounding ambient atmosphere.

In an application of the invention, individual samples may be stored inindividual liners in an automatic or manual system for later analysis.The samples are placed in the liner, either directly or on to packingmaterial as normal. The injection septum and cap are then fitted to theliner, and the complete assembly is stored in a storage container. Whenthe sample is to be analysed, the liner, together with its septum andcap, are transferred to the injection port of the gas chromatograph, andsealed in place.

Injections are made into the liner and, when required, the liner iseasily removed by reducing the gas pressure in the injector, removingthe sealing force and simply withdrawing the liner manually orautomatically, for example, with a magnet.

Various embodiments of the invention are now described, though by way ofillustration only, with reference to the accompanying diagrammaticDrawings in which:

FIG. 1 shows a front view of a simple gas chromatograph system;

FIG. 2 shows a sectional view of a traditional injection liner;

FIG. 3 shows a sectional view of an injection liner according to theinvention and fitted with a septum and cap;

FIG. 4 shows a sectional view of another injection liner of theinvention, this one having a gas inlet hole and seal;

FIG. 5 shows a sectional view of a complete injector containing theinjection liner of FIG. 3, where gas is to be supplied externally;

FIG. 6 shows detail at the top of the injector of FIG. 5;

FIG. 7 shows a sectional view of a complete injector containing theinjection liner of FIG. 4, where gas is to be supplied from within theinjection system;

FIG. 8 shows detail at the top of the injector of FIG. 7;

FIGS. 9,10,11 show a sequence relating to the use of an injection systemlike that of FIG. 5;

FIG. 12 shows the use of an injection system like that of FIG. 7;

FIGS. 13,14 show a sequence relating to the removal of a liner of theinvention;

FIG. 15 shows a front view of an automatic gas chromatograph systemusing automatic storage and removal of the liner.

The gas chromatograph (1) shown in FIG. 1 consists of a column oven (2),in which the column (3) is mounted. At one end the column is connectedto the injector (4), which is mounted in its own heated environment. Atthe other end the column is connected to the detector (5), which is alsomounted in its own heated environment. The chromatograph is controlledvia a keypad (6) and display (7). Signals from the detector 5 areamplified in the chromatograph and transferred to the data system (8),shown here as a computer.

Samples are injected into the injector 4 using the syringe (9), and aretransported through the column 3 by carrier gas, separating in thenormal chromatographic way. They emerge from the column 3 into thedetector 5 as separated components.

A conventional liner is shown in FIG. 2. It consists of a glass, quartzor silica tube (10) filled with a packing material (11) and shaped (12)to improve the performance of the liner.

A liner of the invention is shown in FIG. 3. The new liner consists of aglass, quartz or silica tube (13). It also contains packing (14), and isshaped (15) to improve its performance. A shaped section (18) is builtinto the tube, forming an outwardly-projecting laterally-extendingflange, so that the septum (16) can be housed on it and held gas tightin place by the septum cap (17).

A liner according to the invention and suitable for use where carriergas can be supplied from within the injector is shown in FIG. 4. Thisembodiment of the new injection liner is provided with a gas inlet hole(19) and an O-ring seal 21 mounted within a locating channel defined bytwo walls (20).

FIGS. 5 and 6 show the use of a liner of the invention in a situationwhere carrier gas is to be supplied externally to the injector.

The complete injector consists of an outer tubular body (24) connectedto a top (25) and a base (26). The column 3 is fitted into a tee piece(27) one arm of which is connected to the base of the injector 26 via aconnecting tube (28), and sealed in place with a nut and ferrule (29),while the other arm of which is connected via a line (30) to acontrollable gas supply (not shown).

The injection liner 13 fits within the tubular body 24 of the injector,and is held sealed in place at the top by a downward force from apressure plate (31). This seals the tube 13 to the injector top 25 bythe O-ring (23) because of the downward force transmitted through theseptum cap 17. An insulating component (32) prevents contact between theseptum cap 17 and the injector top 25, and also serves to ensure theoptimal compression of the O-ring 23.

A split line (33) permits gas to flow out of the injector after it haspassed up the annular space (34) between the liner 13 and the body 24,as required for normal split and split-less operation.

The remainder of the injector consists of an outer case (35), whichpermits cooling gas to be blown into the bottom of the injector (36) andout through the top (37). The injector can be heated by applying avoltage across the two electrical connections (38). This voltageresistively heats the body 24 of the injector, and hence the liner 13.Temperatures are controlled. using the signal from a temperature sensor(39).

The section (40) is shown separated from the rest of the syringe 9. Inoperation this section can either be part of the syringe or the end of agas supply line.

An alternative embodiment is shown in FIGS. 7 and 8, where the injectoris able to supply the carrier gas directly. In this case, the injectionliner shown in FIG. 4 is used. This has the integral gas inlet hole 19,profiling 20 and seal 21. In this embodiment the injection liner 13 fitswithin the tubular body 24 of the injector, and is held sealed in placeat the top by a downward force from a pressure plate 31. This seals thetube 13 to the injector top 25 by the O-ring 23 because of the downwardforce transmitted through the septum cap 17. An insulating component 32prevents contact between the septum cap 17 and the injector top 25, andalso serves to ensure the optimal compression of the O-ring 23.

A split line 33 permits gas to flow out of the injector after it haspassed up the annular space 34 between the liner 13 and the body 24, asrequired for normal split and split-less operation.

The seal 21 is held in place by the local profiling 20 of the liner.Optimal compression for this seal is ensured by the design of theprofiling. The seal serves to isolate the zone 34 of the injector, whichis where the gas flows to the split line 33, from the top part of theinjector, where gas can flow in through the inlet pipe 22, via the inlethole 19 to the top of the liner. When required, gas is supplied throughthe inlet pipe 22, and is constrained to pass into the injection linerby the two O-rings 21 and 23. It passes into the top of the liner by wayof the hole 19 and then on down the liner, as required

The remainder of the injector consists of an outer case 35, whichpermits cooling gas to be blown into the bottom of the injector 36 andout through the top 37. The injector can be heated by applying a voltageacross the two electrical connections 38. This voltage resistively heatsthe body 24 of the injector, and hence the liner 13. Temperatures arecontrolled using the signal from a temperature sensor 39.

Operation of the system is now described with reference to the sequenceof FIGS. 9-11. Before injection, the body 24 of the injector willgenerally have been cooled. Gas will flow in through the line 30 to thetee 27 supplying the column 3, and at the same time providing an upwardgas flow into the injector via the line 28. From there, this upward flowpasses up the annular space 34 between the liner 13 and the body 24 ofthe injector and out through the split line 33. The liner is held sealedin place by a downward force exerted by the pressure plate 31. A samplemay be contained in the syringe 9, or may previously have been loaded into the liner.

If—see FIG. 10—the sample has not been pre-loaded into the liner, thenthe syringe is moved down. It pierces the septum, and is pushed downuntil the tip of the needle reaches the correct position in theinjection liner 13, generally just into the packing material 14. Theplunger of the syringe is depressed at the appropriate rate, and thesample is ejected from the syringe. The syringe is then removed.

FIG. 11 shows the configuration where the injector is incapable ofsupplying the necessary gas. A gas supply pipe (41) is now insertedthrough the septum, and supplies the necessary carrier gas for theseparation. The pressure plate 31 ensures that the liner remains inplace. Gas now flows down through the liner 13 and the packing material14. The temperature of the liner is raised to that required for theevaporation of the solvent by heating the body of the injector 24.During this phase gas continues to flow into the tee 27 from the line30, which continues to supply the column 3 and to supply an upward flowthrough the line 28, thus preventing solvent from entering the column.Both gas flows, from the line 41 and the line 30 pass up the annularspace 34 between the liner 13 and the injector body 24 and out throughthe split line 33. This ensures that the solvent is efficiently carriedaway after its removal from the sample matrix.

In the next phase the split line 33 is closed, and the pressures on thelines 30 and 41 are adjusted so that the flow through the line 30 passesdownwards into the column 3 rather than upwards through the line 28. Gasfrom the line 41 at the top of the liner flows down through the liner,and then flows down through the line 28 and into the separation part ofthe system. A small flow may also be provided inwards through the splitline 33 to prevent sample diffusion into the annular space 34 or theline 33. The body 24 of the injector is then heated to the temperaturerequired to displace the sample from the liner, and the sample passes onto the column, possibly via a cryogenic focusing trap (not shown).

The configuration described for FIG. 11 is maintained during theseparation process.

In the case where the injector is capable of supplying the necessarycarrier gas, the arrangement is as shown in FIG. 12. Gas passes into theinjector via the gas supply pipe 22, and thence into the injectionliner. The pressure plate 31 ensures that the liner remains in place.Gas now flows down through the liner 13 and the packing material 14. Thetemperature of the liner is raised to that required for the evaporationof the solvent by heating the body of the injector 24. During thisphase, gas continues to flow into the tee 27 from the line 30, whichcontinues to supply the column 3, and to supply an upward flow throughthe line 28, thus preventing solvent from entering the column. Both gasflows, from the line 22 and the line. 30, pass up the annular space 34between the liner 13 and the injector body 24 and out through the splitline 33. This ensures that the solvent is efficiently carried away afterits removal from the sample matrix.

In the next phase the split line 33 is closed, and the pressures on thelines 22 and 30 are adjusted so that the flow through the, line 30passes downwards into the column 3 rather than upwards through the line28. Gas from the line 22 flows down through the liner, and then downthrough the line 28 and into the separation part of the system. A smallflow may also be provided inwards through the split line 33 to preventsample diffusion into the annular space 34 or the line 33. The body 24of the injector is then heated to the temperature required to displacethe sample from the liner, and the sample passes on to the column,possibly via a cryogenic focusing trap (not shown).

Whichever configuration is used, and referring to FIG. 13, at the end ofthe separation process the pressure balance in the system is alteredsuch that the pressure at the top of the injector is reduced, and alsogas is supplied upwards through the line 28 and down into the column 3by the line 30. The gas line 41 is then removed if this configuration isbeing used. Gas continues to be supplied to the column, and up throughthe line 28 via the line 30. An extractor device (42) for removing theliner, such as an electromagnet, is applied to the top of the liner,and—as shown in FIG. 14—the liner 13 is removed, together with its 16,cap 17 and O-ring 23. The liner can then simply be replaced by insertionof a new liner, reversing the above removal process, followed byre-pressurisation.

This replacement operation can thus be performed with ease, either afterevery analysis or after a series of analyses have been carried out.

A fully automatic gas chromatography system, fitted with an automaticinjector 43, is shown in FIG. 15. This injector controls the position ofthe injection mechanism (44) in all three axes, using motors and drivesin tracks (45).

The injection mechanism 44 houses a conventional syringe 9, a gas supplypipe 41 (if required), and an electromagnet 42. Samples are stored inpre-loaded injection liners (46) in a storage rack (47) before analysis.When required, the sample is withdrawn from the rack 47 using theelectromagnet 42 and placed in the injector 4. The pressure plate 31holds the liner in place. The separation process is then carried out asdescribed before under the control of the injector controller (48) andits associated gas and electrical controls (49), all under thesupervision of the computer 8.

After analysis, gas flows are adjusted as previously described, and thepressure plate 31 is removed. The used liner is withdrawn by theelectromagnet 42 and deposited (at 50) in the used liner rack (51).

The integral moulding—the flange at the input end of the liner—whichprovides the ability to fit the septum and septum cap, thus allows avery simple way of exchanging liners, both manually and automaticallyThis enables the User to replace the liner whenever required, even asfrequently as once per sample.

What is claimed is:
 1. An injection liner for use in the injector of agas chromatograph, the liner being in the form of an elongate tubehaving an input end and an output end, the input end bearing alaterally-extending external flange.
 2. An injection liner as claimed inclaim 1, wherein the liner's output end is associated with arestriction.
 3. An injection liner as claimed in claim 2, wherein theflange has a number of concentrically-circular ridges on itsseptum-facing surface.
 4. An injection liner as claimed in claim 3,wherein the liner includes a special gas input aperture positionedbetween its ends and between this aperture and the liner's output endthere is exterior sealing means.
 5. An injection liner as claimed inclaim 4, wherein the sealing means is an O-ring, suitably mounted aroundthe exterior of the liner between ridges on the outside of the liner. 6.An injection liner as claimed in claim 1, wherein the flange has anumber of concentrically-circular ridges on a surfacing facing away fromsaid tube.
 7. An injection liner as claimed in claim 1, wherein theliner includes a special gas input aperture positioned between its endsand between this aperture and the liner's output end there is exteriorsealing means.
 8. An injection liner as claimed in claim 7, wherein thesealing means is an O-ring suitably mounted around the exterior of theliner between ridges on the outside of the liner.
 9. An injection liner,as claimed in claim 1, in combination with an injection septum, arrangedto fit over the liner's input end and to fit sealingly against theliner's flange, and a closure cap arranged to fit tightly over andaround the septum and the flange so as to hold the septum sealinglyagainst the flange and close the input end.
 10. An injection liner asclaimed in claim 9, wherein the input end has a thread thereon and theclosure cap screws thereonto.
 11. An injection liner combination asclaimed in claim 10, wherein the septum is a disc-shaped object matchingthe dimensions of the liner's flanged input end and made of a siliconerubber protected by a coating on each side in the form of a layer ofpolytetrafluoroethylene (PTFE).
 12. An injection liner combination asclaimed in claim 10, wherein the closure cap is made from, or encloses,magnetic material.
 13. An injection liner combination as claimed inclaim 12, wherein the closure cap extends in use laterally beyond theboundaries of the tube and flange and provides a sealing surface.
 14. Aninjection liner combination as claimed in claim 10, wherein the closurecap extends in use laterally beyond the boundaries of the tube andflange and provides a sealing surface.
 15. An injection linercombination as claimed in claim 9, wherein the septum is a disc-shapedobject matching the dimensions of the liner's flanged input end and madeof a silicone rubber protected by a coating on each side in the form ofa layer of polytetrafluoroethylene (PTFE).
 16. An injection linercombination as claimed in claim 15, wherein the closure cap is madefrom, or encloses, magnetic material.
 17. An injection liner combinationas claimed in claim 16, wherein the closure cap extends in use laterallybeyond the boundaries of the tube and flange and provides a sealingsurface.
 18. An injection liner combination as claimed in claim 15,wherein the closure cap extends in use laterally beyond the boundariesof the tube and flange and provides a sealing surface.
 19. An injectionliner combination as claimed in claim 9, wherein the closure cap is madefrom, or encloses, magnetic material.
 20. An injection liner combinationas claimed in claim 19, wherein the closure cap extends in use laterallybeyond the boundaries of the tube and flange and provides a sealingsurface.
 21. An injection liner combination as claimed in claim 9,wherein the closure cap extends in use laterally beyond the boundariesof the tube and flange and provides a sealing surface.